The present invention relates to an electronic control apparatus, and more particularly to an electronic control apparatus equipped with a drive circuit for selectively controlling electric power supply to a driving objective.
According to a conventional electronic control apparatus, a switching type drive circuit is installed to selectively control electric power supply to a driving objective, such as an electronic element or an electric load, by turning on and off a switching element.
For example, the Japanese patent No. 2572408 or the Japanese patent No. 3368783 discloses a charge pump (charge-up) circuit for producing a high voltage by charging/discharging a capacitor. Another conventional drive circuit is, for example, a switching regulator (switching type power source circuit), or an electric load drive circuit for selectively driving an external electric load.
Especially, according to an electronic control apparatus, there is the tendency that electric power consumption increases in accordance with highly advanced functions. In this respect, adoption of a switching type drive circuit is effective in reducing the electric power loss. Meanwhile, an advanced electronic control apparatus incorporates numerous and various circuits.
In view of effectively installing numerous components, it is preferable to use a multilayered laminated printed board having as a plurality of wiring layers.
According to a switching type drive circuit, the current flows in a power supply path extending from the power source wiring to the ground wiring with a steep change in the rising-up or falling-down stage.
When such a pulse current is large and periodic, electromagnetic waves will be emitted as noises resulting from current changes from the wiring pattern of a printed board which serves as the power supply path of an electronic control apparatus, or from the wire harness of a power supply path which serves as the power supply path existing outside the electronic control apparatus. For example, in an automotive vehicle, the electromagnetic waves will give adverse effects to a radio or other electric wave receiving devices installed on this automotive vehicle. Furthermore, the electromagnetic waves will give adverse effects to other circuits in the electronic control apparatus.